1. Technical Field
The present invention relates to an optical reproducing device and an optical reproducing method.
2. Related Art
In holographic data storage, binary digital data “0” and “1” are made into a digital image (signal light) as “bright” and “dark”, the signal light is Fourier-transformed by a lens, and an optical recording medium is irradiated with the signal light. Then, a Fourier transform image is recorded as a hologram in the optical recording medium. In order to realize high recording density, it is necessary to increase the degree of multiplexing and increase the data amount per page (page data amount).
However, there is the problem that, when the degree of multiplexing and the page data amount increase, the affects of crosstalk noise and scattering become larger, and the signal-to-noise ratio (SNR) of the reproduced image ends up greatly dropping.
In order to address this problem, the present applicant proposes a method which, by performing a two-time reproducing operation, obtains two reproduced images depending on whether or not there is a direct current component from one Fourier transform hologram that has been recorded and, by comparing those two reproduced images, reduces noise that is common to both.